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25 lines
845 B
Scheme
25 lines
845 B
Scheme
;; deletion.scm -- list deletion utilities
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;; Copyright (c) 2009 Alex Shinn. All rights reserved.
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;; BSD-style license: http://synthcode.com/license.txt
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(define (delete x ls . o)
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(let ((eq (if (pair? o) (car o) equal?)))
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(if (eq? eq eq?)
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(let lp ((ls ls) (rev '())) ;; fast path for delq
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(let ((tail (memq x ls)))
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(if tail
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(lp (cdr tail) (take-up-to-reverse ls tail rev))
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(if (pair? rev) (append-reverse! rev ls) ls))))
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(remove (lambda (y) (eq x y)) ls))))
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(define delete! delete)
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(define (delete-duplicates ls . o)
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(let ((eq (if (pair? o) (car o) equal?)))
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(let lp ((ls ls) (res '()))
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(if (pair? ls)
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(lp (cdr ls) (if (member (car ls) res) res (cons (car ls) res)))
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(reverse! res)))))
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(define delete-duplicates! delete-duplicates)
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